1. Field of the Invention
The invention relates in general to an automatic paper feeding apparatus, and more particularly to an automatic paper feeding apparatus whose frictional roller has several frictional surfaces.
2. Description of the Related Art
Currently, printer, copier or multi-functional machine normally achieves automatic paper feeding by an automatic paper feeding apparatus 100 as indicated in FIG. 1. The automatic paper feeding apparatus 100 is used in a printer. When the printer receives a printing instruction, the automatic paper feeding apparatus 100 mainly moves a top paper P contained in a paper carrying plate 130 by the paper-taking roller 110. The paper-taking roller 110 is designed to take the topmost sheet of paper. However, as the frictional coefficients between different varieties of paper are different, the design cannot cover a full range of variety. Therefore, a frictional plate 120 is needed for feeding the paper. When the paper-taking roller 110 moves the top paper P, only the topmost top paper P will enter the paper track 140 situated in the left side for subsequent printing, avoiding the occurrence of paper jam. An elastic member Sp is used for adjusting the distance between the frictional plate 120 and the paper-taking roller 110.
To assure that each time only one sheet of top paper P is sequentially fed into the paper track 140. The frictional coefficients between the paper-taking roller 110, the frictional plate 120 and the top paper P satisfy the expression: u1>u3>u2, wherein u1 is the frictional coefficient between the surface of the paper-taking roller 110 and the top paper P, u3 is the frictional coefficient between the frictional plate 120 and top paper P, u2 is the frictional coefficient between two sheets of top paper P.
However, the frictional plate 120, contacting paper and wearing out gradually, has an average printing capacity of 50,000 sheets of paper. After that, the user has to contact the supplier to replace the frictional plate. Therefore, there is a need for larger printing volume. For example, a laser printer has a printing volume of more than 100,000 sheets of paper.